Potentiometer



Oct. 29, 1957 G. J. MUCHER ETAL POTENTIOMETER Filed Sept. 30, 1955INVENTORS e f Marker gr map/ 14W m BY 6:0 kw: WWI m ATTORNEYS UnitedStates Patent POTENTIOMETER George J. Mueller, Rochester, N. H., andGeorge L. Chapman, York, Maine, assignors to Clarostat Mfg. Co., Inc.,Dover, N. H., a corporation of New York Application September 30, 1955,Serial No. 537,801

9 Claims. (Cl. 201-48) This invention relates to a structurally andfunctionally improved potentiometer and especially a unit of thischaracter incorporating an improved design whereby its phase may bevaried.

It is a primary object of the invention to provide a structure wherebythe phasing of an assembly involving a single or ganged potentiometer(or similar control) may be accomplished externally, without disturbingthe relative axial or radial positions of the parts constituting suchcontrol. Additionally, where a series or gang of controls are connectedto a single shaft, the adjustment of one or a number of these controlsmay be readily achieved without disturbing the phasing of other controlsincluded in the assembly.

A further object is that of providing a structure in which theadjustment which may be resorted to in one control will not set updistortion stresses in that or adjacent controls. Accordingly, the userwill not have to be apprehensive as to the changing of the electricalcharacteristics of an assembly when adjusting the parts.

Moreover, an adjusting and locking mechanism will be included in theunit as constructed in accordance with the present teachings, and whichwill permit of that unit having its parts secured against accidentalshifting such as might occur as a consequence of continuous vibration towhich the control is subjected.

A still further object resides in the designing of a potentiometer orsimilar unit which will include relatively few parts, each individuallysimple and rugged in construction, capable of ready production andassembly to furnish any desired number of units which may beindividually adjusted insofar as phasing is concerned with theexpenditure of minimum effort and time.

With these and other objects in mind, reference is had to the attachedsheet of drawings illustrating one practical embodiment of theinvention, and in which:

Fig. l is a partly sectional side view of a ganged assembly ofotentiometers;

Fig. 2 is a plan view of such an assembly with certain of the partsremoved;

Fig. 3 is a transverse sectional view taken along the line 3-3 in thedirection of the arrows as indicated in Fig. 1;

Fig. 4 is a fragmentary plan view of a part of a single assembly andshowing the elements of the same in separated condition;

Fig. 5 is a fragmentary sectional view under one extreme of the range ofadjustment which is permissible; and

Fig. 6 is a perspective view of the shield which preferably forms a partof the mechanism.

Referring primarily to Fig. 1, the numeral 10 indicates in each instancea cylindrical casing which may be formed of metal arranged in effect inthe form of an enclosing band. One edge of this band may embrace areduced flange portion to be overlapped by an adjacent band so that theparts can be secured against movements with respect to each other as,for example, by bolts 11. End plates or caps 12 and 13 may close theouter faces 2,811,620 Patented Oct. 29, 1957 of the end casings 10 of aganged assembly. Plate 13 conveniently carries a conventional bearingportion 14' within which a shaft 15 has bearing. That shaft may becommon to and operate all of the control units in a given assembly. Ofcourse if only a single unit is present, then caps or plates such as 12and 13 may close the opposite side faces of the same and providerotatable support for the shaft 15.

Forming a part of each of the controls is a rotor assembly which willcooperate with a resistance 16. That resistance as illustrated,conveniently takes the form of an insulating strip around which the wireconvolutions of a resistance coil are wound. The rotor assembly may,

by way of illustration, include a hub portion 17 secured againstmovement with respect to shaft 15. That hub will preferably be formed ofinsulating material and carry adjacent one of its ends a contact ring18. Adjacent its opposite end it will support an actuating plate 19. Thelatter has applied to it a contact grouping conveniently embracing aring 20 from which an arm 21 extends to engage the windings of theresistance strip 16. A bridging part is electrically connected with ring26 and includes a strip 22 terminating in ring 18. The latter is engagedby a contact arm 23.

An inner casing 24, conveniently formed of insulating material, issupported in sliding contact with the inner face of casing 10. Casing 24mounts the resistance 16 which is preferably fixed with respect to it.This casing is also provided with a terminal board or block 25 which maybe integral with it and extend beyond its outer annular face. Terminals26 are supported by the board or block and may in the usual manner beconnected with current leads. These terminals will, for example, beconnected with the contact arm 23, the ends of the resistance 16 and oneor more other desired points in the length of that resistance.

At a point adjacent that at which the terminal board or block 25 extendsfrom the inner casing 24, casing 10 is provided with an opening 27. Thelength of this opening is greater than the length of the portion 25. Toone side of this opening a key plate 28 is secured by, for example,bolts. Extending from this plate, is a threaded shank 29 which mayreceive a clamping nut 30. Thus, the board 25 may extend through opening27 and a limited relative rotation of casing 10 with respect to innercasing 24 may be effected (for example, 10).

A shield 31 conveniently embracing an arcuate strip of metal is providedand has a curvature corresponding to that embraced in the outer face ofcasing 10. This strip is furnished with an arcuate slot 32, the lengthof which is substantially equal to that of terminal block or board 25. Asecond slot 33 parallels slot 32. The width of this second slot is suchthat it may receive therein key plate 28. Its length is such that theplate may have limited travel therein. Adjacent the ends of slot 32, theshield includes outwardly extending tongue portions or flanges 34. Theshield being preferably of metal, these tongue portions will incorporatea limited amount of flexibility and resiliency. They should preferablyincline towards each other to a small extent. The length of the slot 32being equal to the terminal board or block 25 and the tongues beingprovided, it follows that as the parts are assembled, these projectingportions will bear one against each of the end faces of unit 25.Accordingly, the shield 31 will normally not be movable with respect toinner casing 24.

A spring member, preferably in the form of a resilient strip 35 isprovided. That member should have a length substantially greater thanthe length of slot 33. Also, this strip should have a smaller radiusthan that of the shield member 31 or casing 10. It is provided with acentral opening 36 which is smaller than nut 30 but permits of thepassage of stem 29 therethrough. In conclusion, while considering thisstructure, it is to be noted that shield 31 incorporates a lengthsubstantially greater than open ing 27 of the casing so that even if theparts are relatively adjusted to occupy one or the other extremeposition, this opening will still be obstructed or covered by theshield.

Now considering the structure and operation of a single control unitinvolving, for example, the detailed structure described, it will beunderstood that the resistance strip 16 is provided and mounted withinthe inner casing 24 so as to be secured against movement with respect tothe same. The ends of the resistance may connect to proper terminals 26of the block or board 25. This inner casing is disposed within an outercasing such as 10 and with the part 25 extending through the opening 27of the latter. The rotor assembly is secured to the shaft and the latterhas rotatable bearing in one or both of the end plates 12 and 14.Contact arm 23 will be secured to a second terminal 26 and as aforebrought out others of these terminals may be electrically connected tosuitable points in the length of the resistance strip. With currentflowing through the terminals, it will also flow through the arm 21,resistance 16, ring 18 and arm 23. As the shaft is turned the resistancevalue will be varied.

The shield member 31 will have been applied over the terminal block orboard 25. The indicia on this shield may designate the various terminals26. The flanges or tongues 34 will bear against the ends of the blockand the inner face of the shield will ride in contact with the outerface of casing 10. Under these circumstances, stem 29 and plate 28 willextend through slot 33. It will be assumed that nut St) has beenloosened so that while spring strip or member 35 bears against the outerface of shield 31, the engagement will only be with minimum pressure.'Also it will be assumed that the operator desires to change the phasingof the control or, in other words, effect an adjustment of theresistance with respect to the outer casing.

With casing 10 stationary, a thrust exerted on the shield 31, one of theends of block or one of the terminals 26 will cause them to function asactuating means and result in inner casing 24 being rotated within outercasing 10. This will, of course, shift the resistance 16 with respect tothe parts of the rotor assembly thereby rephasing the control. Duringthis shifting of the parts, the shield 31 cannot be accidentallydetached because strip 35 is bearing against the same and this strip isheld against detachment from the stem 29 by nut 39. After the operatorhas shifted the parts to the desired extent and as determined bysuitable instrument tests, he will lock those parts against subsequentshifting. This is accomplished by tightening nut 39 or its equivalent.

With such tightening, strip 35 is caused to intimately bear adjacent itsend portions in frictional contact with the outer face of the shield. Ineffect, it functions as a brake-shoe against the shield with the latterserving as a drum. All stresses will be outwardly insofar as stem 29 isconcerned. That stern being secured to the outer casing 10, nodistortion will be transmitted by these stresses to the inner casing andto the resistance contained therein. These stresses have heretoforeresulted in defective operation where a variable phasing of anelectrical control Where strains are transmitted to the internal parts.

In the case of a ganged assembly, as shown in Figs. 1 and 2, it is ofcourse apparent that adjustments to individual controls will in no wiseaffect the shaft common to those controls and the rotor assembliesmounted by that shaft. The key plate or equivalent abutment will limitthe adjustment to a maximum range which might be required under extremeconditions. ,That range might be greater or less than 10 to each side ofa center position. The shield 31 will, in all instances, cover theopening 217,

The same will be true of the strip 35 with respect to slot 33. It isapparent that, for example, a centrally disposed unit in an assembly mayhave its phasing adjusted without disturbing the electrical valuespresent in end units. The reverse is also true. Consequently an operatormay,

7 with assurance, adjust each individual control in a ganged assemblyand correlate the same to other controls therein with assurance thatnone of the difficulties inherent to attempted solutions of the presentproblem, and as heretofore practiced, will come into being.

Thus among others, the several objects of the invention as specificallyaforenoted are achieved. Obviously numerous changes in construction andrearrangements of the parts may be resorted to without departing fromthe spirit of the invention as defined by the claims.

We claim:

1. In a potentiometer assembly, in combination a rotatably mountedcasing, a terminal block extending therefrom, a shielding member formedwith an opening receiving said block, an outstruck part included in saidmember adjacent said opening and bearing against a surface of said blockto retain said member fixed with respect thereto, a fixed casinginterposed between said first-named casing and said member and meanscarried on said fixed casing and bearing against said member forsecuring said casings against movement with respect to each other.

2. In a potentiometer and similar assembly in combination an outercasing, an inner casing secured within said outer casing for rotationtherein, a resistance rigidly supported within the inner casing, meansconnected to the latter and extending beyond said outer casing wherebysaid inner casing may be rotated with respect to said outer casing forphasing said assembly, locking means connected with said rotating means,said locking means including a brake element, means connecting the sameto said outer casing, a unit including a drum surface connected to theinner casing to move with the same and means for pressing said elementsinto engagement with the surface of said unt.

3. In a potentiometer and similar assembly in combination an outercasing, an inner casing secured within said outer casing for rotationtherein, a resistance rigidly supported within the inner casing, meansconnected to the latter and extending beyond said outer casing wherebysaid inner casing may be rotated with respect to said outer casing forphasing said assembly, locking means connected with said rotating means,said locking means including a shield bearing against said outer casingand connected to move with said inner casing and a resilient unitbearing against said shield and connected to said outer casing.

4. In an assembly as specified in claim 3, said resilient unitcomprising a strip formed with an opening, a stem extending from theouter casing and passing through said opening and means secured to saidstem for varying the pressure on said strip.

5. In an assembly as specified in claim 3, a terminal block extendingfrom said inner casing through an opening in said outer casing, saidshield being formed with an opening through which said block extends andcertain edges of said block bearing against certain edges of saidopening whereby said shield moves as a unit with said block.

6. In an assembly as specified in claim 5, upstruck portions forming apart of said shield and defining said opening thereof and said upstruckportions yieldingly bearing against the adjacent surfaces of said block.

7. In a potentiometer and similar assembly in combination a contactmember rotatable in a circular path, a substantially circular resistanceengaged thereby, means mounting said resistance for movement in a pathcorresponding to that of the contact member, actuating means connectedto said mounting means for moving the latter and said resistance, saidactuating means extend-ing outwardly from and in a direction radial tosaid resistance,

5 a stationary casing enclosing said mounting and formed with an openingthrough which said actuating means projects and means for obstructingsaid opening to prevent casual access through the latter.

8. In an assembly as defined in claim 7, said obstructing meanscomprising a shield connected to move with said actuating means and saidshield covering the opening of said casing.

9, In an assembly as defined in claim 7, and means locking said mountingagainst movement, said locking means being supported by said casing toact against said obstructing means.

References Cited in the file of this patent UNITED STATES PATENTS

